Page 207, address D503, André wonders if there's not a bug as a JSR D7BD seems to be repeated very closely.
It is also listed as an uncorrected bug page 571.

This is not a bug.
Actually, the code here is trying to validate the drive letter asked by the user. But there are two ways to ask for a drive:
1- entering "A-" (or B- or C- or D- ) will set the default drive to the chosen letter. Any file load attempt will be made from this default drive
2- loading a file specifying the drive where it's stored, therefore bypassing the default drive, for instance: LOAD"B-ZAKMCKRAK" will load the file ZAKMCKRAK on the drive B, whatever the default drive is (and providing Chema has ported the game )

So the two JSR D7BD are there for these two ways of asking for a drive: one will just be used to load a file, the other will set the default drive. They are two different entries, each one requiring (more or less, but that's another story) the JSR D7BD.

Last edited by Symoon on Fri Dec 04, 2015 11:15 pm, edited 1 time in total.

In other words, the book explains that in a file catalog entry, bits 0 to 5 of a dedicated byte are the most significant bits of a file size (in occupied sectors). So displaying this size would use 8 bits + bits 0 to 5 = up to 14 bits.

This seems unlikely, it should rather be bits 0 to 3 (so 12 bits), leading to a maximum size of 4096 sectors, which is 1MB. Don't think any disk would hold such a big file!
Also, page 278, address #E331, is an AND#0F (mask 00001111), proof that only 4 bits are used.
This has also been tested by setting the 5th bit to 1: DIR doesn't show any file size change, but altering the 3rd bit instead affects the displayed size indeed.

So actually, bit 4 and bit 5 were unused. Bit 5 is now dedicated to flag a directory (in the Sedoric directories demo).(This mistake was explained in the CEO-Magazine looong ago)